Insulating paper – natural ester insulation oil characteristics at different moisture and ageing level
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Date
2019-06
Authors
Muhammad Fariz Bin Ahmad Shukri
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Abstract
The ageing behaviour of Kraft transformer insulating paper in natural ester virgin coconut oil (VCO) at different moisture was compared with the ageing behaviour of Kraft transformer insulating paper in mineral oil (MO), also, at different moisture. The aim of the study is to investigate the effect of moisture in natural ester VCO and the transformer MO at different ageing level. The Kraft paper and the dielectric fluid, natural ester VCO and petroleum-based MO, were aged at 90C for 0, 168, 336, and 504 hours at different moisture level. In this research study, the oil samples of VCO and MO were prepared with five different moisture condition in which, 0 ppm, 10 ppm, 30 ppm, 100 ppm and out-of-container moisture condition. In dry condition test, the sample of Kraft insulating paper were prepared for breakdown strength and tensile strength test while for in-oil test, the samples of Kraft paper were immersed in VCO and MO for breakdown strength and viscosity test. The breakdown voltage of the VCO and MO were tested with the oil test unit and the breakdown voltage of the Kraft transformer insulating papers were also tested using in-oil breakdown strength test unit. This research found that, the samples of VCO show minimal color change as compared to samples of MO when tested according to America Standard for Testing and Materials (ASTM) D1500. The tensile strength of the paper were tested using Single Column Universal Test Machine with force capacity of 500N. The results obtained from this test found that, breakdown strength of natural ester VCO is almost 50% much higher compared to petroleum-based MO. Indeed, viscosity of VCO is also twice as higher than MO. This experiment findings also show that after the ageing process, the viscosity is said to be almost constant for both MO and VCO. The presence of moisture in VCO doesn’t affects the dielectric properties of VCO as compared to MO. The samples of Kraft insulating paper impregnated in VCO show almost 50% higher breakdown strength as compared to samples impregnated with MO. Moreover, the samples of Kraft paper impregnated in VCO show better tensile strength retention with 90% tensile strength retention as compared to MO only 50% over ageing period. The characteristic breakdown strength of VCO alone and VCO impregnated paper was found to be, on the average, better than that of MO alone and MO impregnated paper.